The fact that certain jobs use a combination of hourly wages and tip to determine compensation is less about "service" but more about helping the owner tie compensation to revenue. The more customers, the more the owner can afford to pay the employee. But rather that give the worker a commission on the customers they served, they pay a low hourly rate, and the servers earn a commission from the customers in the form of a tip. This aligns employee compensation with owner revenues.

Compensation is a tricky area. Using day care centers as an example, wouldn't it make more sense to compensate day care workers based on the number of children rather than hourly or using tips. The more children the more the day care workers made and more the day care center could afford to pay them.

The same is true with educators. Would educators be willing to accept compensation based on class size and standard testing scores achieved by their students?

While there is a "service" component to tip, most people pay within a pretty narrow range, so unless service is terrible, tips work mostly as "variable compensation" tied to volume.

Gifts given to people over the holidays are totally different. They are an expression of thanks from the giver to the recipient. They have no relationship to tips.